Fix­ing The 2017 CRF450RX

BIG RED WANTS TO GO OFF-ROAD RAC­ING

Dirt Rider - - 2018 Sherco Se-rs And Sef-rs - STORY BY AL­LAN BROWN PHO­TOS BY BROWN DOG WIL­SON

Honda’s 2018 CRF450RX is a com­pletely new mo­tor­cy­cle, so there was cer­tainly a lot to learn about it. In the 30 hours I’ve put on the bike, I’ve found some ar­eas that needed fix­ing for me and saw what first the stock ad­just­ments, and then what Pro Cir­cuit, could do to help.

The pre­vi­ous-gen­er­a­tion CRF450R 2009–2016 en­gine was good, but some peo­ple seemed to think it was a lit­tle slow. This new gen­er­a­tion of en­gine is cer­tainly not slow. Ac­tu­ally, the RX’S power is al­most too re­spon­sive, to the point it can be a bit of a hand­ful at times. This is the same en­gine and trans­mis­sion as the 450R model with just one-tooth-big­ger (50T) rear sprocket; the bike has a very no­tice­able on/off jerky feel­ing with a throt­tle that can be good for mo­tocross but not as good on tighter sin­gle­track. The bar-mounted map se­lec­tor’s three set­tings (1 be­ing stan­dard, 2 softer/ trac­tion, and 3 ag­gres­sive) do make a no­tice­able dif­fer­ence; af­ter rid­ing the bike only a few hours I set­tled on the sec­ond map.

We only had a few op­tions when we went look­ing for an ex­haust. Pro Cir­cuit had just com­pleted its new dual ex­haust sys­tem for the 450RX and of­fered to let us test one of its com­plete sys­tems. The Pro Cir­cuit guys gave us a stain­less-steel ex­haust that is a tad bit heav­ier than stock but of­fers great per­for­mance and dura­bil­ity. Fit­ment was spot-on and in­stal­la­tion was easy. I im­me­di­ately no­ticed two things: The power was much broader and the bike was no­tice­ably qui­eter. The Pro Cir­cuit muf­flers fea­ture re­mov­able spark ar­restors, which we left in (the OEM muf­flers do not have spark ar­restors, as this is a com­pe­ti­tion off-road model, not a green­sticker bike). Leav­ing the spark ar­restors in helped make the bike qui­eter and made the power much more us­able, and that’s what we were go­ing for in the first place. Un­less you plan on only rid­ing this bike at a track I would rec­om­mend leav­ing the spark ar­restors in.

I found my­self al­most never us­ing first gear. The 450RX has the same close-ra­tio gear­box as the 450R, and I feel like the RX would ben­e­fit from a wider-ra­tio gear­box. Since that was not an op­tion for us to change, I opted for a smaller rear sprocket. Sim­ply go­ing down to a 49-tooth rear sprocket al­lowed me to use first gear a lit­tle more and made sec­ond very good.

The 450RX is not ex­actly a feath­er­weight; how­ever, under nor­mal con­di­tions it does not feel overly heavy. Honda has long been work­ing on a “cen­ter mass” prin­ci­ple to try to get the most amount of weight to the mid­dle of the bike just be­low the rider. The more I rode this bike the more I started to feel like maybe big red has gone too far in this di­rec­tion. Af­ter spend­ing some time tun­ing the en­gine

there was still a very no­tice­able teeter­tot­ter feel­ing with the on/off throt­tle po­si­tion. It’s not that there is an un­usual amount of en­gine-brak­ing; it’s more like all of the weight is too cen­tered. The sim­plest way I found to help re­duce this sen­sa­tion was to just turn the idle up a lit­tle.

Now that we had tuned in the en­gine and power de­liv­ery I wanted to start work­ing on the chas­sis, which is even more im­por­tant than the mo­tor.

I rode the bike at sev­eral dif­fer­ent lo­ca­tions, in­clud­ing open desert, tighter sin­gle­track, and a few mo­tocross tracks be­fore start­ing to make any changes. The bike seemed to be more at home on a mo­tocross track than off road or trails. The chas­sis has a light feel­ing that is easy to turn, and it loves to climb hills. The light and nim­ble feel­ing is good on lower-speed tight sec­tions, but the op­po­site is true for faster sec­tions and steep down­hills. At medium speeds I strug­gled with the front-wheel trac­tion quite a bit, mainly not be­ing able to steer the bike where I wanted it. At higher speeds there can be some head­shake if you are not com­pletely com­mit­ted to ac­cel­er­a­tion or heavy brak­ing. I also no­ticed the bike seems to han­dle bet­ter with a full tank of gas ver­sus a near-empty one. But the stock bike’s big­gest weak­ness is fast, steep down­hills; this is where the chas­sis was at its worst. And over­all, it’s some­what of an un­bal­anced bike.

There was no doubt the sus­pen­sion was much softer than the 450R’s—it was es­pe­cially no­tice­able on the mo­tocross track—and I felt that was hold­ing the bike back a lit­tle. Yes, I know this is an off-road bike, but I rode it ev­ery­where to help find its strengths and weak­nesses. Keep in mind Honda built this bike to be a com­pe­ti­tion model for rac­ing GNCC, WORCS, Hare Scram­ble, and even mo­tocross events for the right rider.

So next up to tune was the sus­pen­sion. The fork and shock are Showa, same as the 450R, but with off-road valv­ing and a softer shock spring. I started by stiff­en­ing the ad­justers on the rear shock—go­ing from 3-1/4 out on the high-speed com­pres­sion to 1-1/2, and from 14 to 10 clicks out on low speed. This helped hold the rear of the bike up, with the goal be­ing to trans­fer more weight to the front wheel. I also worked with the shock’s re­bound ad­juster; how­ever, go­ing only two clicks slower be­gan to make the shock feel harsh. I stiff­ened up the fork three clicks also to help re­duce bot­tom­ing on big­ger hits. The bike be­gan to han­dle bet­ter but lost some com­fort in the rocks, as well as made the front and rear de­flect and be­come a lit­tle dif­fi­cult to keep under you.

Af­ter sev­eral rides and quite a bit of clicker ad­just­ing I felt like I had hit a dead end. I knew the bike had more po­ten­tial, but not be­ing sure what di­rec­tion to go next I de­cided to get help. Since Pro Cir­cuit had al­ready been test­ing with the JCR rac­ing guys I fig­ured it would have some good set­tings for this bike. Its guys gave the bike a full revalve, along with a stiffer shock spring, go­ing from a 5.3 to 5.5 (5.5 is stan­dard on the 450R model), and put on their shock link­age pull rods.

Since we were mak­ing a few sus­pen­sion up­grades I opted to get a lit­tle more ag­gres­sive with the tires. I put on Dun­lop’s MX3S front and the new MX3S 18-inch rear (stock are Dun­lop AT81 tires).

Nat­u­rally, my first im­pres­sion was, “Way bet­ter.” With the new shock set­tings and stiffer spring the bike felt a lit­tle stinkbug at first, even with 108mm of sag. Pro Cir­cuit sug­gested clos­ing the re­bound a lit­tle on the shock. Af­ter a few rides and clos­ing the re­bound to nine the bike felt fairly bal­anced. Front-wheel steer­ing was im­proved, as I feel the stiffer shock spring does help trans­fer more weight to the front. Bot­tom­ing re­sis­tance was way bet­ter, and the bike could be pushed much harder into ob­sta­cles. The down­hill han­dling was also im­proved but still not to the point where I would say this bike likes to charge down steep hills. One area that might have got­ten a lit­tle worse was flat, rocky sec­tions; but this was not sur­pris­ing af­ter stiff­en­ing up the valv­ing and shock spring.

I would like to see some­one make a heav­ier fly­wheel for this bike. I feel like that would im­prove the power de­liv­ery and also the han­dling. The over­all en­gine char­ac­ter­is­tic is that of a light fly­wheel; typ­i­cally a heav­ier fly­wheel can help with rear-wheel trac­tion and a more torquey power char­ac­ter. As for the chas­sis, a heav­ier fly­wheel could make the bike feel more pre­dictable with less of the un­bal­anced, teeter-tot­ter feel­ing.

This is a race­bike, not a trail­bike. If you want a bike you can ride at the track and not have to swap the tank or rear wheel to go trail rid­ing, then this bike might be for you. If you are be­low an ad­vanced B-level rider, this bike is prob­a­bly too ag­gres­sive to be your off-road ma­chine. If you are a top B-level or bet­ter rider, you might like this bike. If you are pro-level racer, you might re­ally like this bike. It re­wards those with very good rid­ing tech­nique with its quick and re­spon­sive han­dling.

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